Flowmeter materials for a beverage machine

ABSTRACT

A flowmeter, in particular for a beverage preparation machine, includes a housing, such as a moulded housing, delimiting a measuring chamber, and a measuring body, such as a moulded body, rotatably mounted in the measuring chamber. The housing and the measuring body are made of at least one of polyoxymethylene, polyformaldehyde or polybutyleneterehpthalate.

This application is a 371 filing of International Patent ApplicationPCT/EP2010/058690 filed Jun. 21, 2010. FIELD OF THE INVENTION

The field of the invention pertains to flowmeters, in particularconstitutive materials of flowmeters for beverage preparation machines.

For the purpose of the present description, a “beverage” is meant toinclude any liquid food, such as tea, coffee, hot or cold chocolate,milk, soup, baby food, etc.

BACKGROUND ART

Certain beverage preparation machines use capsules containingingredients to be extracted or to be dissolved; for other machines, theingredients are stored and dosed automatically in the machine or elseare added at the time of preparation of the drink.

Various beverage machines, such as coffee machines, are arranged tocirculate liquid, usually water, from a water source that is cold orheated by heating means, to a mixing or infusion chamber where thebeverage is actually prepared by exposing the circulating liquid to abulk or pre-packaged ingredient, for instance within a capsule. Fromthis chamber, the prepared beverage is usually guided to a beveragedispensing area, for instance to a beverage outlet located above a cupor mug support area comprised or associated with the beverage machine.During or after the preparation process, used ingredients and/or theirpackaging is evacuated to a collection receptacle.

Most coffee machines possess filling means that include a pump forliquid, usually water, which pumps the liquid from a source of waterthat is cold or indeed heated through heating means, such as a heatingresistor, a thermoblock or the like. For instance, U.S. Pat. No.5,943,472 discloses a water circulation system for such a machinebetween a water reservoir and a hot water or vapour distributionchamber, for an espresso machine. The circulation system includesvalves, a metallic heating tube and a pump that are interconnected witheach other and with the reservoir via a plurality of silicone hoses thatare joined together by clamping collars.

To control the characteristics of the liquid circulated to the mixing orinfusion chamber, e.g. quantity and/or speed, such machines typicallyinclude a flowmeter. The flowmeters used in such beverage machines aremade of food safe materials at least where exposed to the circulatingfluid and have to be economically affordable to be used in suchmachines.

For instance, EP 0 841 547 discloses a flowmeter commercialised byDIGMESA which is suitable for beverage preparation machines. Thisflowmeter has a two-part housing with a bayonet connection, the housingcontaining an inner measuring chamber with a central fixed shaftextending therethrough for mounting an inner rotatable measuring bodywith fins that are located in the flow path and that are driven thereby.The flow of liquid passing through the measuring chamber is derived froma measure of the speed of rotation of the rotatable measuring body usinga Hall sensor. A drawback of this device lies in the large frictionsurface between the fixed shaft and the rotating measuring body whichchanges depending on the orientation of the flowmeter and which alsoaffects the accuracy of the measure of the flow through the chamber.

U.S. Pat. No. 4,666,061 discloses a similar flowmeter for beveragedispenser lines for wine, mineral water or beer that can be easilydisassembled and reassembled for cleaning. The flowmeter has a two-parthousing assembled by a bayonet connector and enclosing a measuringchamber. The chamber contains a centred rotatable measuring body havinga rotatable shaft held in pace by a pair of facing diamond pointbearings mounted into the housing and extending into the chamber. Adrawback of this device lies in the price of the diamond point bearingsand the required assembly steps for mounting such point bearings intothe housing of the flowmeter.

Hence, there is still a need to provide an accurate inexpensiveflowmeter, in particular for use in a beverage preparation machine.

SUMMARY OF THE INVENTION

The invention thus relates to a flowmeter, in particular for a beveragepreparation machine. The flowmeter comprises: a housing, such as amoulded housing, delimiting a measuring chamber; and a measuring body,such as a moulded body, rotatably mounted in the measuring chamber. Thehousing and the measuring body are made of at least one of POM and PBT.

In particular, the housing and the measuring body are respectively madeof POM (e.g. polyoxymethylene or polyformaldehyde), as Schulaform 9A,and PBT (e.g. polybutylenterephthalate), such as Tecdur GK30, or viceversa. Hence, the housing may be made of POM and the measuring body ofPBT, or the housing may be made of PBT and the measuring body of POM.

In so far as the flowmeter is used in a beverage preparation machine,the materials forming the chamber and the rotatable measuring body withthe shaft should be food safe. Furthermore, they should have a lowfriction coefficient and a low abrasion rate and be well controllable inthe manufacturing/moulding process so as to achieve high dimensionalprecision to provide a high quality flowmeter at limited cost. Moreover,these materials should be so controllable in the manufacturing process,e.g. moulding, as to permit the formation of small-sized reliable partsto be able to reduce the size of the device in which such a flowmeter isintegrated for use. All these requirements are fulfilled by using theabovementioned materials, in particular in combination.

The abrasion rate of the POM material against the PBT material can be ofabout 0.2 μm/km. The abrasion rate of the PBT material against the POMmaterial is typically of about 0.7 μm/km. Moreover, such POM and PBTmaterials are food safe. Such an abrasion rate provides a long lifetimefor inexpensive moulded flowmeters, e.g. for use in beverage preparationmachines.

In an advantageous embodiment, the moulded housing and/or the mouldedmeasuring body include a stabilising filler, such as beads, inparticular glass beads. In this case, the composite material, includinga filler and a POM or PBT binder, can be used to manufacture thecorresponding part of the flowmeter. The stabilising filler mayrepresent 10 to 70 vol % of said housing and/or the measuring body (3),in particular 15 to 50 vol % such as 20 to 40 vol %.

The use of a filler material such as beads leads to an increased controlof the shrinkage of the composite material when it consolidates duringthe moulding step. This is particularly desirable for insuring a highdimensional precision of the relatively movable parts and for a properassembly of the parts. Moreover, the use of beads instead of fibres,e.g. glass fibres, as a filler material provides clean surfaces whichcan be manufactured with tight tolerances in particular for thebearings. Furthermore, the use of beads as a filler material reduces thefriction coefficient and abrasion rate compared to the use fibrematerial as a filler. The components produced from such a compositematerial also exhibit a high stability, in particular for the connectingpart, as discussed below.

Typically, the housing is made of two assembled moulded bodies, thehousing having in particular a cup-like body and a cover body. Forinstance, the cup-like body has a rim and the cover body has a seal lip,the seal lip being force-fitted into the rim, or vice versa, for sealingthe cover body on the cup-like body.

In an embodiment, the rotatable measuring body has a rotatable shaftextending across the measuring chamber, the shaft being rotatablymounted and positioned in the measuring chamber at opposite extremitiesof the shaft by point bearings. For instance, the shaft is a rotor orlike element with flow intercepting parts such as fins or blades,typically an impeller. Each point bearing may be formed of a protrudingpart and a cooperating facing counter-part part, in particular arecessed part, associated, respectively, with the housing and anextremity of the rotatable shaft, or vice versa. The protruding part andthe counter-part are advantageously integrally formed with theirassociated moulded housing and moulded rotatable shaft.

In one embodiment, the housing comprises facing protrusions extendinginto the chamber for forming the point bearings. Alternatively, theprotrusions may be located on the shaft of the measuring body. It isalso possible to provide a mixed configuration, i.e. a first bearingwith the protrusion on the shaft and a second (opposite) bearing withthe protrusion on the housing.

The rotatable shaft typically has a rotation axis that extends between apoint bearing located at a cover body of the housing and a facing pointbearing located in a cup-like body of the housing.

The cup-like body may have a rim forming a reference surfaceperpendicular to the shaft's rotation axis, the cover body having aninner face that is urged against the reference surface for preciselysetting a spacing between these point bearings so as to hold and allowfree rotation of the shaft therebetween.

The bodies forming the housing can be assembled by a snap, latch, clampor hook arrangement, in particular by a bayonet connection.

Thus, the manufacturing costs of such flowmeter that does not require adiamond element for the bearing are significantly reduced. The twobearing parts can be formed during a moulding step of the componentsthey are respectively associated with. The bearing parts can beintegrally formed with the static support component and with the movingmeasuring component, respectively, and no separate assembly step isrequired therefor which limits the production costs. The accuracy of theflowmeter is however largely independent from the orientation of theflowmeter. The protruding part and/or counter-part of each point bearingcan be made by fusion/solidification and/or polymerization of materials,usually by moulding these materials.

Each of the moulded bodies forming the housing may have athrough-opening communicating with the measuring chamber for circulatingliquid through such flowmeter.

The housing can include a connecting arrangement for disconnectablyconnecting a sensor device thereto, in particular a Hall sensor device.

The invention also relates to a beverage preparation machine having aliquid circulation circuit, in particular a water circulation circuit,that comprises a flowmeter as described above.

For instance, the machine is a coffee, tea or soup machine, inparticular a machine for preparing within an extraction unit a beverageby passing hot or cold water or another liquid through a capsule or podcontaining an ingredient of the beverage to be prepared, such as groundcoffee or tea or chocolate or cacao or milk powder. The machine maycomprise a brewing unit for housing this ingredient. Typically, themachine includes one or more of a pump, heater, drip tray, ingredientcollector, liquid tank and fluid connection system for providing a fluidconnection between the liquid tank and the brewing unit, etc. Theconfiguration of a fluid circuit between the liquid reservoir and aheater for such a machine is for example disclosed in greater details inco-pending application PCT/EP08/067072.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described with reference to the schematicdrawings, wherein:

FIG. 1 shows an exploded view of a flowmeter according to the invention,the assembled flowmeter being shown in FIG. 2;

FIG. 3 illustrates part of an electric connector for such a flowmeter;and

FIG. 4 illustrates part of the housing of such a flowmeter.

DETAILED DESCRIPTION

FIGS. 1 and 2 illustrate a flowmeter 1 typically for a beveragepreparation machine such as a coffee machine. The flowmeter may bemounted in the fluid circuit of the beverage preparation machine as forexample described in greater details in PCT/EP09/053368.

Flowmeter 1 has a housing formed of two assembled moulded bodies 2,4delimiting an internal generally cylindrical measuring chamber 10. Forexample, the housing is formed by injection moulding.

Housing 2,4 contains a rotatable measuring body 3 in the form of a rotoror impeller. Body 3 has a series of radial members 31, e.g. fins orblades, on a rotatable shaft 32 extending centrally across the measuringchamber 10. Shaft 32 has a lower part 33 from which radial members 31extend and an upper part 34. Two cavities 35 are provided in upper part34 for housing a pair of magnets 36 of corresponding shape. Shaft 32 orbody 3 may be manufactured by injection moulding as well

Flowmeter 1 has upper and lower point bearings for mounting oppositeextremities 32′,32″ of rotatable shaft 32 in housing bodies 2,4. Thesepoint bearings are formed by protrusions of housing 2,4 extending intochamber 10 and by recesses in extremities 32′,32″ of rotatable shaft 32forming a positioning counter-part for the protrusion, a lowerprotrusion in the form of a pin 11 and an upper recess 37 of this typeforming part of the lower and upper bearings can be seen in FIG. 1. Thelower and upper bearings are identical to ensure similar performance inall possible orientations.

Protrusions 11 and counter-parts 37 are integrally formed with themoulded housing bodies 2,4 and the rotatable shaft 32, respectively. Inother words no additional component is needed for forming the bearingparts of the flowmeter. These may be moulded directly with therespective components, i.e. housing bodies 2,4 and shaft 32. The shaftor even the entire impeller 3 (except magnets 36) can be made of POM;housing 2,4 can be made of PBT with 30 vol % glass beads as a filler.

As illustrated in FIG. 1, lower housing body 4 is in the general shapeof a cup and upper housing body 2 is in the general shape of a cover. Itis understood that the lower and upper orientation merely refer to theparticular orientations of the flowmeter as illustrated in the Figures.During use, flowmeter 1 may take any orientation or even changeorientation.

Rotatable shaft 32 has a rotation axis 3′ that extends between a pointbearing (not shown) located at cover body 2 and a facing point bearing11 located in cup-like body 4.

Cup-like body 4 has a rim 41 forming a reference surface 42perpendicular to rotation axis, cover body 2 having an inner face 22that is urged on reference surface 42 for precisely setting a spacingbetween the point bearings 11 so as to hold and allow free rotation ofshaft 32 therebetween.

Furthermore rim 41 has an upright inner surface 43 cooperating with acorresponding seal lip 23 of cover body 2 for sealing cover body 2 oncup body 4 by force-fitting of lip 23 into the rim 41. This assembly isshown in greater details in the cross-section of FIG. 4, in which thesame numeric references designate the same elements. A hatched part 23′illustrates the deformation of lip 23 due to the force fitting. In avariation, lip 23 and rim 41 may be welded, e.g. by ultrasonic welding,in which case hating 23′ would illustrate the welded portions.

Cup-like body 4 has four spaced apart hooks 45 that are evenlydistributed on rim 41 and that cooperate with corresponding passages 25and hook retaining parts 26 at the periphery of cover body 2 to form abayonet connection. As the locking movement of cover body 2 on cup body4 is in a plane perpendicular to shaft 32 and rotational axis 3′, thespacing between the point bearings is not affected by this locking. Thisspacing is entirely determined by the geometry (and position) ofreference surface 42 so that tight tolerances for the bearings can beprovided even though they are formed by moulding and not by additionaldiamonds.

Each of the moulded bodies 2,4 has a through-opening communicating withmeasuring chamber 10 for circulating liquid through such flowmeter. Atubular inlet 47 is provided in cup-like body 4 and a tubular outlet 27is provided in cover body 2. The inlet and the outlet could of course beswitched. Moreover, the inlet and the outlet could be located on thesame moulded body.

Furthermore, cover body 2 has a socket 28 with a cavity 29 for receivinga sensor plug 5 as shown in FIG. 2, the plug itself being illustrated ingreater details in FIG. 3 in which the same numeric references designatethe same elements.

Sensor plug 5 has a housing 51 which may be closed with a lid orotherwise sealed (not shown). Housing 51 has a pair of front hooks 52for securing plug 5 in cavity 29 and delimits an inner chamber 53.

Chamber 53 contains a Hall sensor on a PCB 54 with cables 55 forconnection to a control unit (not shown), for instance of a beveragepreparation machine such as a coffee machine. To achieve a safeinsulation of the PCB from any liquid circulating via chamber 10, atriple barrier is provided: the walls of socket 28 in cover body 2,housing 51 of plug 5 and a Kapton or other polyimide foil around PCB 54,whereby PCB 54 with the Hall sensor is safely sealed.

The Hall sensor, PCB 54, housing 51 and cavity 29 are so arranged andpositioned that when plug 5 is secured in socket 28, the Hall sensor issituated above extremity 32″ with magnets 36.

PCB 54 may be formed as part of a main board of the control unit towhich cables 55 are connected. Hence, PCB 54 may be manufacturedtogether with the control unit and then separated therefrom, e.g. cutaway or broken off along a weakened line, before or after assembly ofplug 5 before or after connection of cables 55, and then secured withplug 5 into socket 28. Hence, the manufacturing of the sensor device andits control unit can be simplified and optimised. In some embodiment,the flowmeter may even be mounted directly onto the main board so thatPCB 54 is an integral part of the main board and remains an integralpart of the main board of the control unit, for instance as illustratedin greater details in WO 2009/043865 and in PCT/EP09/053368.

During use of flowmeter 1, liquid is circulated from inlet 47 to outlet27 via chamber 10. The flow of liquid will be intercepted by blades 31thus driving shaft 32 in rotation about axis 3′ between the pointbearings at extremities 32′,32″ of shaft 32. The speed of rotation ofshaft 32 will be proportional to the flow of liquid in chamber 10 anddriving measuring body 3. By rotating shaft 32, magnets 36 are rotatedadjacent to the Hall sensor on PCB 54 that will detect the rotatingmagnetic field generated by the magnets and convert it into acorresponding electric signal having a frequency corresponding to thespeed of rotation of shaft 32. The information regarding the flow ofliquid will then be communicated to a control unit via cables 55.

What is claimed is:
 1. A flowmeter comprising: a housing, delimiting ameasuring chamber; and a measuring body rotatably mounted in themeasuring chamber, wherein the housing and the measuring body arerespectively made of polyoxymethylene (POM) andpolybutyleneterephthalate (PBT) or vice versa.
 2. The flowmeter of claim1, wherein the housing is a moulded housing and the measuring body is amolded body.
 3. The flowmeter of claim 1, wherein the housing, themeasuring body, or both include a stabilizing filler.
 4. The flowmeterof claim 3, wherein the stabilizing filler comprises glass beads.
 5. Theflowmeter of claim 3, wherein the housing contains 10 to 70 vol % of thestabilizing filler or the measuring body contains 15 to 50 vol % of thestabilizing filler.
 6. The flowmeter of claim 1, wherein the housing ismade of two assembled molded bodies, with the housing having a cup-likebody and a cover body.
 7. The flowmeter of claim 6, wherein the cup-likebody has a rim and wherein the cover body has a seal lip that isforce-fitted into the rim, or vice versa, for sealing the cover body onthe cup-like body.
 8. The flowmeter of claim 1, wherein the rotatablemeasuring body has a rotatable shaft extending across the measuringchamber, the shaft being rotatably mounted and positioned in themeasuring chamber at opposite extremities of the shaft by pointbearings.
 9. A flowmeter comprising a housing, delimiting a measuringchamber; and a measuring body rotatably mounted in the measuring chamberand having a rotatable shaft extending across the measuring chamber, theshaft being rotatably mounted and positioned in the measuring chamber atopposite extremities of the shaft by point bearings, wherein the housingand the measuring body are made of at least one of polyoxymethylene(POM), polyformaldehyde or polybutyleneterephthalate (PBT), and whereineach point bearing is formed of a protruding part and a cooperatingfacing counter-part part associated, respectively, with the housing andan extremity of the rotatable shaft, or vice versa.
 10. The flowmeter ofclaim 9, wherein the counter-part part is a recessed part and areintegrally formed with their associated housing.
 11. The flowmeter ofclaim 10, wherein housing and rotatable shaft are molded parts.
 12. Aflowmeter comprising: a housing, delimiting a measuring chamber; and ameasuring body rotatably mounted in the measuring chamber and having arotatable shaft extending across the measuring chamber, the shaft beingrotatably mounted and positioned in the measuring chamber at oppositeextremities of the shaft by point bearings, wherein the housing and themeasuring body are made of at least one of polyoxymethylene (POM),polyformaldehyde or polybutyleneterephthalate (PBT), and wherein thehousing comprises facing protrusions extending into the chamber forforming the point bearings.
 13. A flowmeter comprising: a housing,delimiting a measuring chamber; and a measuring body rotatably mountedin the measuring chamber and having a rotatable shaft extending acrossthe measuring chamber, the shaft being rotatably mounted and positionedin the measuring chamber at opposite extremities of the shaft by pointbearings, wherein the housing and the measuring body are made of atleast one of Polyoxymethylene (POM), polyformaldehyde orpolybutyleneterephthalate (PBT), and wherein the rotatable shaft has arotation axis that extends between a point bearing located at a coverbody of the housing and a facing point bearing located in a cup-likebody of the housing.
 14. The flowmeter of claim 12, wherein the cup-likebody has a rim forming a reference surface oriented perpendicular to therotation axis of the shaft, the cover body has an inner face that isurged against the reference surface for precisely setting a spacingbetween the point bearings so as to hold and allow free rotation of theshaft therebetween.
 15. The flowmeter of claim 2, wherein the moldedbodies are assembled by a snap, latch, clamp or hook arrangement. 16.The flowmeter of claim 2, wherein the molded bodies are assembled by abayonet connection.
 17. The flowmeter of claim 2, wherein each of themolded bodies has a through-opening communicating with the measuringchamber for circulating liquid therethrough.
 18. The flowmeter of claim1 further comprising a connecting arrangement for disconnectablyconnecting a sensor device to the housing.
 19. A beverage preparationmachine having a circulation circuit for water or another liquid thatcomprises a flowmeter as defined in claim
 1. 20. A beverage preparationmachine having a circulation circuit for water or another liquid thatcomprises a flowmeter as defined in claim 9.